1. Field of the Invention
The invention relates to a backing plate for abrasive flap wheels, having an inner part with a location hole for a shaft of a driving machine and an outer flange for abrasive flaps to be adhesively bonded in place.
2. Description of the Related Art
For a long time there have been backing plates for abrasive flap wheels which are made of a fiber material impregnated with plastic and in which sheet-metal reinforcement is provided around the location hole. These relatively thin backing plates are put onto the shaft, provided with a thread, of a driving machine and screwed tight with a nut. The same type of fastening also exists in abrasive flap wheels in which the backing plates are made of injection molded plastic. In this case, too, only a location hole is provided in the inner part, so that fastening to the machine by means of a nut is necessary.
Such a type of fastening is time-consuming, since, when a wheel is changed, the nut has to be slackened and unscrewed, the new wheel has to be put on and the nut has to be screwed on again. In addition, there is the risk of the nut falling down or of even being lost, which considerably further increases the time needed.
The object of the invention is to design a backing plate for abrasive flap wheels of the type specified further above in such a way that a quick and nonetheless reliable means of fastening the abrasive flap wheels to the driving machine is possible.
According to the invention, this object is achieved by forming the inner part with a hub which has an internal thread for the threaded shaft of the driving machine.
On account of this design, it is possible to screw the abrasive flap wheel in a simple manner onto the shaft, provided with a thread, of the driving machine without locking having to be carried out with an additional nut. The intended direction of rotation of the driving machine runs in such a way as to tighten the abrasive flap wheel upon coming into working engagement with a workpiece. On the other hand, on account of the relatively large diameter of the abrasive flap wheel, it is possible to slacken said abrasive flap wheel by hand without requiring a tool, which was necessary during the fastening by means of the nut.
In an advantageous development of the invention, provision is made for the hub to be designed so as to project beyond the sunk surface of the backing plate and to have a length which essentially corresponds to the distance between the surface of the outer flange and the surface of the sunk inner part.
In order to achieve a reliable fastening, it is advantageous if the internal thread extends over the entire length of the hub. In this case, it is advantageous if the internal thread has at least three thread turns.